For generations, knife sharpeners have been available to sharpen dull knives but without regard to the angle of the knife edge. Knives produced in factories were made largely by artisans who undertook to create a sharp edge without regard to the angle of the edge. Sharpness was the focus and it did not matter to the artisan what the angle was. That was true also after the factory knife was sold, used, and became dull. The owner sought to sharpen the edge somehow, with a tool file, on a sharpening stone, or perhaps with a sharpening “steel”. The angle at which the edge facets were formed by the user was not recognized as important. Factory edge angles were not standardized by any of the large or small knife factories. They did not consider it of any importance, particularly since the user had no sense of the importance of the edge angle and had no means or ability to sharpen the edge at a specified or controlled angle. As a consequence, for generations knife sharpeners have been sold without specifying anything more than “the sharpener will create a sharp edge on your knife”. In general both factory knives and sharpeners have been sold only on the expectation that the resulting knife will be sharp.
The consumer has had no expectations or concerns about the actual angle of the edge—only that it be sharp enough for the job at hand. Examination of the knives produced in Europe shows that the total edge angle varied from about 40 degrees to 60 degrees or larger. American manufacturers have followed the European practices. Asian knives made with smaller edge angles have not been readily available or popular in the United States, but that has begun to change recently.
The European designs of knife edges with their relatively large angles have evolved as a result of their diets and methods of food preparation. In general the European style knife is designed for butchering and to cut tough fibrous foods such as a wide variety of meats.
Knives manufactured in Japan and Asia are found to have edge angles of about 10 degrees to 20 degrees, most commonly about 15 degrees which they have found to be practical for cutting fish and other softer, less tough foods than those encountered in Europe.
The recent interest of the Asian style cutlery has presented new challenges for American knife sharpeners that historically have been designed exclusively for the larger angled European and American, style knives. The Asian knife customer commonly has not been willing to trust his knife to existing European or American sharpeners and he has continued largely to sharpen his Asian knives tediously by hand on sharpening stones.
As a consequence of the confusion created by the introduction of Asian style knives into America, several sharpeners have been offered to handle both Asian and European style knives.
These sharpeners are simply a physical combination of two sharpeners, one for the larger angle European knives and one for Asian style knives incorporated into a single housing. These commonly have one sharpening stage or section dedicated to European blades and another dedicated separate sharpening stage or section to sharpen Asian blades. Such sharpeners are consequently large, very expensive, and produce relatively weak knife edges particularly for the thinner low edge angle Asian blades.
A primary reason why Asian knives have not been popular in America is that American foods are generally more like the Europeans—tougher and more fibrous. It has been shown that lower angle Asian knives as sold commercially do not hold up as well when cutting tougher American foods. The thin 15 degree edge bends over in use and quickly becomes dull.
The attraction of the Asian edge to the American consumer is that it appears to be sharper than when cutting with the European knives. This is because the edge facets are set at a total included angle of only on average 30 degrees or so which will cut easier and in fact feel like a sharper wedge than the 40 degree wedge of the European edge.
Forty degree total angle edges are however stronger, do not fold over so fast and hold up longer when cutting the tougher American type foods. A recognition of the inherent weakness of the thirty degree edge has been a deterrent to wide acceptance of the Asian edges—in spite of the perception they cut with less effort.
These inventors have discovered unique simpler, more compact, less expensive designs for sharpeners that can handle both European and Asian style knives. In spite of their simplicity these new sharpeners create sharper and longer lasting edges for both classes of knives than, for example, any other commercially available manual sharpeners offered to sharpen both classes of knives. Further the new design disclosed here produces precision edges of a quality equal to new factory produced knives.